Therapeutic potential of targeting SHP2 in human developmental disorders and cancers

Specific inhibition of SHP2 suppressed abdominal aortic aneurysm formation in mice by augmenting the immunosuppressive function of MDSCs

AIMS

To address the roles of SHP2 in regulating angiotensin II (Ang II) induced abdominal aortic aneurysm (AAA) and the potential molecular mechanisms.

MAIN METHODS

AAA model was established in apolipoprotein E-deficient (apoE^-/-) mice infused with Ang II. Suprarenal aortic luminal diameters were ultrasonically measured to determine the presentation of AAA in mice. The inflammatory and immunosuppressive factors in serum were detected by ELISA. AAA lesion size, positive macrophages and elastic laminae degradation were examined by histological analysis. Myeloid-derived suppressor cells (MDSCs) were measured by flow cytometry after magnetic bead sorting. Bioinformatics analysis was applied to screen the crucial genes related the progression of AAA.

KEY FINDINGS

Treatment with PHPS1 (SHP2 inhibitor) significantly decreased the vascular diameter of AAA. Histological analysis showed that PHPS1 obviously reduced the Masson positive area, macrophages positive area, as well as the damage rate of elastic laminae. Moreover, PHPS1 suppressed the expression of INF-γ, TNF-α and MMPs, as well as elevated IL-10 and arginase-1 expression. Additionally, PHPS1 enhanced the expression of granulocytic MDSCs (G-MDSCs). By consulting with bioinformatics, STAT3 was selected. In G-MDSCs, PHPS1 stimulation obviously increased the phosphorylation level of STAT3, as well as elevated the protein expression of C/EBPβ and arginase-1. However, the above phenomena can be blocked after Stattic (STAT3 inhibitor) treatment.

SIGNIFICANCE

SHP2 may affect the AAA progression by interfering with expansion and function of MDSCs to regulate the body immunity, which might afford a novel direction for the treatment of patients with AAA.

Identification of Phomoxanthone A and B as Protein Tyrosine Phosphatase Inhibitors

Phomoxanthone A and B (PXA and PXB) are xanthone dimers and isolated from the endophytic fungus Phomopsis sp. By254. The results demonstrated that PXB and PXA are noncompetitive inhibitors of SHP2 and PTP1B and competitive inhibitors of SHP1. Molecular docking studies showed that PXB and PXA interact with conserved domains of protein tyrosine phosphatases such as the β5-β6 loop, WPD loop, P loop, and Q loop. PXA and PXB could significantly inhibit the cell proliferation in MCF7 cells. Our results indicated that these two compounds do not efficiently inhibit PTP1B and SHP2 activity. RNA sequencing showed that PXA and PXB may inhibit SHP1 activity in MCF7 cells leading to the upregulation of inflammatory factors. In addition to PTP inhibition, PXA and PXB are multitarget compounds to inhibit the proliferation of tumor cells. In conclusion, both compounds show inhibition of cancer cells and a certain degree of inflammatory stimulation, which make them promising for tumor immunotherapy.

Targeting a Pathogenic Cysteine Mutation: Discovery of a Specific Inhibitor of Y279C SHP2

An intriguing challenge of drug discovery is targeting pathogenic mutant proteins that differ from their wild-type counterparts by only a single amino acid. In particular, pathogenic cysteine mutations afford promising opportunities for mutant-specific drug discovery, due to the unique reactivity of cysteine’s sulfhydryl-containing side chain. Here we describe the first directed discovery effort targeting a pathogenic cysteine mutant of a protein tyrosine phosphatase (PTP), namely Y279C Src-homology-2-containing PTP 2 (SHP2), which has been causatively linked to the developmental disorder Noonan syndrome with multiple lentigines (NSML). Through a screen of commercially available compounds that contain cysteine-reactive functional groups, we have discovered a small-molecule inhibitor of Y279C SHP2 (compound 99; IC₅₀ ≈ 6 μM) that has no appreciable effect on the phosphatase activity of wild-type SHP2 or that of other homologous PTPs (IC₅₀ ≫ 100 μM). Compound 99 exerts its specific inhibitory effect through irreversible engagement of Y279C SHP2’s pathogenic cysteine residue in a manner that is time-dependent, is substrate-independent, and persists in the context of a complex proteome. To the best of our knowledge, 99 is the first specific ligand of a disease-causing PTP mutant to be identified. This study therefore provides both a starting point for the development of NSML-directed therapeutic agents and a precedent for the identification of mutant-specific inhibitors of other pathogenic PTP mutants.

Medicinal chemistry strategies for the development of protein tyrosine phosphatase SHP2 inhibitors and PROTAC degraders

As a non-receptor protein tyrosine phosphatase encoded by the PTPN11 gene, the Src homology 2 domain-containing protein tyrosine phosphatase (SHP2) is involved in mitogen-activated protein kinase (MAPK) signaling pathway and contributes to immune surveillance via programmed cell death pathway (PD-1/PD-L1). To date, numerous SHP2 inhibitors have been developed, some of them have advanced into clinical trials. Moreover, the first PROTAC degrader SHP2-D26 has been proved to effectively induce degradation of SHP2, which may open a new avenue for targeted SHP2 therapies. In this review, we systematically summarized the development of SHP2 inhibitors with a particular focus on the structure-activity relationships (SAR) studies, crystal structures or binding models, and their modes of action.